Previous attempts have been made to construct devices for moving normally stationary objects around.
Most known devices for moving around carts, washing machines and the like, are difficult to use and require lots of physical strength to move such carts and/or objects over a support surface, such as a floor.
U.S. Pat. No. 2,319,581 to Brownlee et al. discloses an article of furniture having a movable handle which has a locked, engaged position as well as a locked disengaged position for bringing wheels into and out of engagement with the floor. A user must apply somewhat outward and upward force to the Brownlee et al. handle for moving the wheels from the disengaged position to the engaged position. Hence,, considerable upper body strength is required of a user who wishes to move the Brownlee et al. furniture when a heavy object is supported thereon. Likewise, the Brownlee et al. device, being locked in either one of engaged and disengaged positions, will have a tendency to move when left unattended on a sloped support surface in its wheel-engaging position.
U.S. Pat. No. 2,783,055 to Michaud discloses a vertically adjustable wheeled supporting frame for cabinets and the like. The Michaud wheeled supporting frame includes a lever which must be rotated upwardly for causing rollers to engage the floor. A stud is provided on the Michaud device for releasably retaining the lever and locking the wheels in their engaged position. Thus, the Michaud frame has some of the drawbacks of the above-described Brownlee et al. device.
U.S. Pat. No. 2,812,189 to Geldhof discloses a caster jack assembly for automatic washing machines that includes a lever rotatably attached to a frame inserted under washing machines for assisting in the movement thereof. The Geldhof lever is rotatable for movement between respective ones of two locking pins, one locking pin retaining the caster jack assembly in a lowered position in which the washing machine is in direct engagement with the floor, and a second locked position in which the caster jack assembly is used to raise the washing machine off the floor for moving the machine from place to place. A spring is provided in the Geldhof device for acting as a counterweight during the lifting operation for compensating for the weight of the washing machine to be moved and enabling the user to lift the machine for rolling on its casters over the floor with very little manual effort. However, the Geldhof handle must be moved upwardly against the force of gravity.
A two-wheeled mobile workbench is disclosed in U.S. Pat. No. 2,672,349 to Brock. The Brock device includes a rotatable lever which must be moved upwardly by a user in order to force the Brock wheels against the floor for raising the workbench in order to move it to a different location. The Brock device apparently requires a fair amount of upper body strength on the part of the user in order to raise the lever and engage the wheels against the weight of the mobile workbench.
Accordingly, there is a need for a mobile work surface or cart which overcomes the drawbacks of prior art devices. There is a need for a footed cart having normally disengaged wheels which can be operated with relatively little effort on the part of the user, yet which is able to carry heavy loads, has few moving parts for enhancing the reliability thereof, and which automatically returns to its normally ground-engaging, non-moving position when the user is not actively causing the cart to be in its movable or operative mode.
Terms such as "cart" and "ground" are for convenience only, as all table-like devices, movable work surfaces, and platforms, for example, are intended to be within the scope of the invention, and my invention is expected to be usable on all manner of supporting surfaces.